1. Field of the Invention
The present invention is directed to an arrangement for driving a warp beam from the machine main shaft via a stepless adjustable drive with a displaceable coupling element determining the step-up relationship, wherein a setting means displaces the coupling element in as direction to maintain a predetermined thread provision.
2. Description of Related Art
Arrangements of the foregoing type are used in warp knitting machines, weaving looms and the like, in order to provide a plurality of threads at the same time, wherein the provision speed has a predetermined relationship to the machine speed. Herein the rate of rotation of the warp beam must increase with decreasing wind diameter in order to maintain this provision speed.
Drive arrangements of the prior art have been described by Reisfeld, Warp Knit Engineering, 1966, pp. 291-294. These have a worm drive driveable by a cog wheel as setting arrangement for the coupling element of the stepless adjustable drive, which is constructed in the form of a bevel gear. The cog wheel is displaced in one direction or the other by ratchets, which are activated by a mechanical comparison arrangement. It has a target value input which is connected with the input shaft of the bevel gear and an actual value input which is connected with a contact roller on the wind upper surface and displaces the coupling element when the actual and target value deviate from one another.
The use of such a stepless adjustable drive has the advantage that a plurality a warp beams of one machine may be driven by its main shaft. For many applications however the contact roller is not useful since it damages the thread material or because slippage occurs. Furthermore, the use of a contact roller requires substantial effort to build and finance. Since the coupling element only finds its correct position after a control action and this occurs rather slowly, the initial segment of the fabric run contains errors and therefore represents losses in production.
U.S. Pat. No. 4,426,856 discloses a warp beam driven by a motor whose rate of rotation is controllable. The appropriate control arrangement comprises a computer which calculates measuring variables dependent from the length of the rolled on or rolled off threads from several beam data, such as wind diameter and thickness of the wind layer, as well as the angle of rotation of the beam. Then the target rate of rotation of the warp beam drive is calculated from the measuring variable, a signal characterizing the angle of rotation of the main shaft, and a setting value, and a corresponding rotational signal is transmitted to a regulator for controlling the warp beam drive. This requires that each beam is provided with a drive motor.
Therefore an object of the present invention is to provide a stepless adjustable drive, equipped with a drive arrangement of the previously described type, which better serves present needs.